The Secret To Making Great Compost In Winter)

One thing we've learnt in the garden is that turning a compost heap is a bit overrated. Some people swear by it but for us turning is a bit of a last resort. We prefer to build it in layers, keep it covered and let the microbes do their job without us interfering too much. The less we disturb them the better the results. This is our approach all year round but in winter it matters even more. As the weather gets colder the composting process naturally slows down but it doesn't stop. The microbes are still in there, still working but different types of microbes dominate depending on the temperature. But they do need every bit of warmth they can generate. If you go in there with a fork and turn the heap during winter you're letting all that precious heat escape. The warmth has been built up by the busy microbes breaking everything down and once it's gone the colder air can make it very hard to get the temperature back up again. By retaining the heat the compost stays active, the microbes stay nice and comfortable and the whole heap keeps ticking over even when the outside air temperature is freezing. So the priority in winter is simple, don't lose the heat. Then when spring warms things up again everything will speed up. So what else can we do to keep the heap warm? The answer is insulation and one of the best materials for this job is cardboard. We cover our heap with layers of cardboard to trap the warmth inside. What's perfect about cardboard is eventually it becomes compost itself. Unlike plastic sheets or old carpet that you have to take on and off, cardboard is part of the cycle. It protects the heap now and feeds it later. We strip the tape off our delivery boxes, peel away the labels and flatten the cardboard out. Once it's laid out across the top of the heap it holds in the heat. Over time the cardboard softens, gets damp and begins to fall apart. When that happens we tear it up and mix it into the pile. It breaks down quickly and has useful carbon and there's nothing wasted. It's a brilliant example of reusing something that would otherwise go into the recycling and if you want to know what's really going on inside the compost use a compost thermometer. Push it into the middle of the heap and it will tell you if there's still warmth in there. It's a quick and easy way to check that the microbes are still active even on those frosty days. The biggest challenge for composting over winter is maintaining a balanced heap. The leaves are falling, you're pruning shrubs, cutting back hedges and it's very easy to go overboard filling your bins with dry leaves and woody trimmings. You really want to aim for a roughly equal mix of green and brown materials. Greens are moist nitrogen-rich materials such as lawn mowings in green weeds which are in short supply over winter and browns are your carbon-rich materials which are plentiful but can cause the heap to dry out and take much longer to break down than fresh green materials especially when the temperature is low. But you don't need to let the brown materials go to waste. One of the best ways around this is to start stockpiling your fallen leaves to make leaf mold. I gather the leaves and add them to big bags rather than adding them to the compost pile. Then I leave them to rot down quietly on their own. Within a year or two you'll have soft crumbly leaf mold that's fantastic for mulching borders or mixing into potting soil and if you need some browns for the compost bin then add some to the bin instead. Either way works well. So what actually goes into the heap in winter? The good news is you can carry on adding most the same things you do in summer. The heap might be working more slowly but it still needs to be fed. Kitchen waste is perfect. All the fruit and veg peelings, apple cores, potato skins, coffee grounds, eggshells and even that bag of wilted salad hiding at the back of the fridge can go straight in. Mr Sheffield's house plant trimmings and spent floral arrangements are ideal too for some extra greens. Evergreen trimmings are another option. They're tougher and can be acidic but if you chop them into smaller pieces and mix them well with other waste they'll eventually break down. And if you can get hold of some steaming hot fresh manure it's one of the best winter additions you can make because it brings warmth as well as nutrients. So do keep your feed in your pile but just remember to keep it balanced. Now for a surprising one, tea bags. A lot of people including us toss them in without thinking but many brands still contain plastic which won't break down. If you're prepared to switch to plastic-free bags or loose leaf tea. If you're wedded to a brand like me then don't add them to your compost. Now this is the bit we learn the hard way. If you throw big chunks into a one winter compost heap like this and they'll still be sitting there untouched when the daffodils start to bloom in spring. So the smaller you can chop things the easier life is for the microbes working hard to decompose your heap, especially your hedge clippings and your woody prunings. But even your green materials like sunflower stalks should be snipped down to size before they go in to give the microbes a helping hand. The same goes for kitchen scraps, banana skins, avocado shells, broccoli stems and those tougher peelings will break down more quickly if you cut them smaller first. Smaller pieces mean quicker decomposition and a healthier more active heap all winter long. Covering your compost not only keeps it nice and cozy, it also protects it from the great British weather. If your compost heap gets soaked it quickly turns into a slimy airless mess. The goal is moisture like a wrung out sponge, damp but not dripping. In summer the danger is drying out but in winter it's drowning. The problem is that too much water pushes out all the air pockets. When that happens the good microbes that need oxygen can't survive, they slow right down or die off and that leaves the door open for the wrong kind of microbes to take over. These anaerobic microbes thrive without oxygen and they're the ones responsible for that stink people sometimes associate with compost. But the solution is simple, always cover the top and if you haven't got a lid like ours a tarp sheet will do the trick. In the summer you shouldn't have too much of a problem getting your heap to heat up provided that you've got the right balance of greens and browns. In winter though it's a bit trickier. Heaps in winter don't always get hot enough to kill off weed seeds or diseases and this can be a problem when you start spreading your compost around your garden. Unless you're confident that you can get your heap back up to temperature in spring and summer we'd avoid throwing in weeds that have gone to seed or any diseased plants. Instead play a bit safer and stick to kitchen scraps, healthy clippings and safe greens and browns. Save the trickiest stuff for when your heap is hotter and more active. Another way to make winter composting easier is to use more than one heap. If you've got the space for two bins or a double or even a triple bay dedicate one to fresh material and then let the other rest. That way you're not constantly disturbing the heap that's already busy breaking down. In winter especially this can make a big difference. You can keep feeding one pile with kitchen waste and gardening trimmings while the other gets on quietly cooking away. By spring the resting pile will be much further along and you won't have wasted the heat and energy your microbes work so hard to build. If you want to make sure you don't undo all your hard work we've made a video on the most common composting mistakes people make. Watch that next and you'll keep your heap on track all year round.